2860QM is the best CPU at 45W. The two available Extreme CPUs (2920XM and 2960XM) both have a 55W TDP - and according to CPUBenchmark.net only the highest clocked one (which is just 100 MHz faster than the 2860QM - the 2920XM has the same base clock but a slower turbo) has a higher benchmark than the 2860QM. More heat and cost are the drawbacks. The decision is yours...

Also even if you upgrade, your graphics card is bottlenecking you. If you are using for heavy gaming, the Nvidia 4200M may well be the one limiting your performance. Almost all laptop GPUs are simply not powerful enough to run the latest games in ultra graphics.
Build a cheap dual Xeon system and use desktop graphics instead for gaming. As for workstation, I don't think you need anything more powerful than that and the prices are very ridiculous. (3820QM is also much more expensive than 3720QM) I guess you could try planting a T530 motherboard instead and deal with keyboard firmware issue. Your drives, fan and RAM should work fine in the new motherboard.

theterminator93 wrote:2860QM is the best CPU at 45W. The two available Extreme CPUs (2920XM and 2960XM) both have a 55W TDP - and according to CPUBenchmark.net only the highest clocked one (which is just 100 MHz faster than the 2860QM - the 2920XM has the same base clock but a slower turbo) has a higher benchmark than the 2860QM. More heat and cost are the drawbacks. The decision is yours...

The cpubenchmark.net score difference between the i7-2760QM and the cpu's mentioned, is a nominal 8%. The scores range from 6650 - 7200.

Some applications can be offloaded to a remote machine, where you can get a machine with a Xeon E5-26x0 cpu scoring 14000 for $200.

When upgrading a laptop CPU I always factor in heat and power consumption. That's because I use my laptops away from home. At home, nothing beats a desktop with 32 GB ram, powerful GPU card, IBM Model M keyboard, dual 27" FHD IPS monitors and more storage than I know what to do with. The 3570K Ivy Bride CPU will outperform pretty much any laptop CPU.

Laptops for me are tools for the road. Battery life is more important than CPU power. The OP's laptop is pretty powerful already. I wouldn't upgrade the CPU but rather save that money towards a desktop or small form factor PC in a tight space.

I also think there's some unreasonable expectations of what you can do on battery here.

The T420/520 almost veers towards the W520 where you are trading off portability and battery for performance... remember these are 2nd gen. laptops so even with a fresh battery and an ultrabay i do not expect a real world 4hrs of work.

These have always been DTR type units.

Even if you buy something newer in these 7 generations we have I think a laptop in this class will burn power unless you want to move to an ultrabook which then would not suit the avg. person here.

TonyJZX wrote:The T420/520 almost veers towards the W520 where you are trading off portability and battery for performance... remember these are 2nd gen. laptops so even with a fresh battery and an ultrabay i do not expect a real world 4hrs of work.

Actually - with the slice battery I had no issues using my W520 to do audio editing while I waited for my wife to go through a medical conference late last year, which lasted 6 hours. I only used about 50% of the total battery capacity - I depleted the main 9C battery and tapped about 10% of the slice battery's capacity - translating to 10-12 hours of real life usage with the "big battery" solution and 5-6 hours with a standard 9 cell only.

Now for someone doing CPU and GPU intensive CAD type work, I certainly agree... 2-3 hours on the 9 cell would be my guess, though 4-6 with the slice. The T420, T520 and W520 don't work with the ultrabay battery - only the slice (The T420s doesn't work with the slice but does work with the ultrabay battery). But then again, even with the newer CPUs like 50 and 60 series... where they really shine is better battery life while doing light work. Load them up and they eat through the battery just as fast as a 20 series will.

One problem also is if you have 2820qm and these powerful processors, you have to make sure the heatsink is clean enough and the paste is good. My friend has thay very machine with 2820qm and after 3 years of league gaming, the paste went so bad that it ended up with 75 degrees on idle and 1fps in gaming (with that throtting and the CPU is still alive)